1. Field of the Invention
The present invention relates to an organic electroluminescent module and a method of manufacturing the same, particularly to an organic electroluminescent module that can be readily manufactured and has high accuracy of touch sensing and a method of manufacturing the same.
2. Description of Related Art
Examples of traditional planar light sources include light emitting diodes (LEDs) provided with lightguide plates and organic light emitting diodes (OLEDs) (hereinafter also referred to as “organic electroluminescent element”).
Since about 2008, the use of LED light sources provided with lightguide plates, which have been typically used as illuminating lamps for general use, has been rapidly spread to the backlights of main displays (e.g., liquid crystal displays (LCDs)) for smart devices (e.g., smartphones and tablets) which have been widely used around the world.
LED light sources, which are used as backlights for main displays, are also used as backlights for common function key buttons provided in lower portions of smartphones.
Some common function key buttons are provided with three marks indicating “Home” (e.g., represented by a square mark) “Back” (e.g., represented by an arrow mark), and “Search” (e.g., represented by a magnifier mark).
In view of high visibility, such common function key buttons are provided with LED light sources with lightguide plates. Such a lightguide plate has a dotted polarizing pattern conforming to the pattern of the mark to be displayed and has LED light sources at the edges. The LED light sources emit light on the side surfaces of the lightguide plate. Light from the LED light sources enters the lightguide plate from the side surfaces and then is totally reflected on the reflection surface of the polarizing pattern toward the front of the lightguide plate. Consequently, light with a predetermined pattern is emitted from the front side of the lightguide plate, so that the viewer sees light with such a pattern when viewing the lightguide plate from the front (see Japanese Unexamined Patent Application Publication No. 2012-194291, for example).
Aside from this, use of surface-emitting organic electroluminescent (EL) panels has been studied to achieve low power consumption and uniform luminance. In use of such an organic EL panel, a cover glass with a printed mark on one surface is prepared and the organic EL panel is disposed on the other surface of the cover glass so as to overlap the printed mark for image display.
Smart devices require touch technology. For this reason, capacitance touch sensing devices are generally disposed on the rear surfaces of cover glasses for display areas and common function keys of smart device.
In many cases, touch sensing devices for such use each include two films having the same size as the cover glass. Touch sensing devices including two glass layers are also used in smart devices with unlimited thickness. Many of the current smart devices employ capacitive sensing technology. Main displays often employ “projected capacitive sensing technology” with an electrode pattern consisting of fine traces extending in x- and y-axis directions. This technology allows “multi-touch operation” where multiple touches can be detected at the same time.
With the use of such touch sensors, traditional common function keys are provided with light-emitting devices that cannot sense touch. The recent emergence of in-cell and on-cell displays, however, has brought a demand for common function keys with touch-sensible light-emitting devices.
Common function keys require surface capacitance technology that allows on/off detection, rather than multi-touch technology. The surface capacitance technology requires a simple solid electrode pattern for touch sensing.
Technology to provide a touch-sensible organic EL panel is also known in which a capacitance sensing circuit is integrated in a flexible printed circuit (FPC) designed to drive the organic EL panel.
A typical single-sided organic EL panel has an electrode to be electrically connected to the FPC. The electrode is on the opposite side to the light-emitting side of the organic EL panel, which means that the FPC is on the opposite side to the light-emitting side. If a capacitance sensing circuit is integrated in the FPC, the circuit is on the opposite side to the light-emitting side of the organic EL device (on the rear side of the organic EL device). In this configuration, the organic EL element has an anode, a cathode, and a protective metal layer in front of (more proximal to the light-emitting surface than) the sensing circuit. This hinders the sensing circuit from detecting variations in capacitance and decreases the accuracy of touch sensing.
One approach for solving such a problem is to form a contact piece by providing a cutout on the periphery of lands (to be electrically connected to the organic EL panel) of the FPC in such a manner that the FPC body with a sensing circuit is disposed on the light-emitting side of the organic EL device, while the contact piece is bent to be disposed on the opposite side of the organic EL device. This approach maintains high accuracy of touch sensing in the sensing circuit and enables connection between the FPC and contact electrodes on the back (on the opposite side of the light-emitting side) of the organic EL panel.
Unfortunately, manufacturing such an organic EL module requires the step of bending the module at a boundary between the FPC body and the contact piece to dispose the contact piece on the back of the organic EL panel, resulting in increased steps of manufacturing the organic EL module.